Since we discovered the NF-kappaB transcription factor in 1986, it has emerged as a key activator of inflammatory and immune responses with important pathologic roles in cancer, heart disease and autoimmune diseases. For these reasons, understanding the details of the control of NF-kappaB and of its transcriptional capabilities has great medical as well as biological significance. In the proposed work, we will take four approaches to deepening our understanding of NF-kappaB. First, we will further investigate the roles of the various forms of the DNA binding site for NF-kappaB, the kappaB site. We have recently observed that particular kappaB sites are highly conserved over evolutionary time, implying that each contains information within every one of its nucleotides, a conclusion that was very surprising given the wide variety of sites that exist in the genome. We propose various approaches to understanding what information is encoded by the various kappaB sites. Our second goal is to use modeling tools combined with experimental tests to better understand the pathways that control NF-kappaB activation and repression. The third approach is to concentrate study on one protein, A20, which is known to play a role in limiting NF-kappaB activation. The turning off of NF-kappaB is as important as its activation, because it of its enormous pathologic potential, and A20 is an important protein in this regard. We have a clue that A20 might be involved in inhibiting a key protein modification that is important for NF-kappaB activation and we will follow that up in many directions. The fourth approach is to study an activator of NF-kappaB that has thus far been neglected, the B94 protein. Here we have made only minimal progress thus far but we outline a variety of methods of attack using genomic and proteomic tools.